Turbo charged engines utilize a Charge Air Cooler (CAC) to cool compressed air from the turbocharger, before it enters the engine. Ambient air from outside the vehicle travels across the CAC to cool intake air passing through the inside of the CAC. Condensate may form in the CAC when the ambient air temperature decreases, or during humid or rainy weather conditions, where the intake air is cooled below the water dew point. When the intake air includes recirculated exhaust gasses, the condensate can become acidic and corrode the CAC housing. The corrosion can lead to leaks between the air charge, the atmosphere, and possibly the coolant in the case of water-to-air coolers. Condensate may collect at the bottom of the CAC, and then be drawing into the engine at once during acceleration increasing the chance of engine misfire.
Other attempts to address condensate formation include restricting intake air travelling through the CAC or restricting ambient air flow to the CAC. One example approach is shown by Craig et al. in U.S. Pat. No. 6,408,831. Therein, the intake air temperature is controlled by an ambient air flow restriction system and an intake air flow restriction system. A controller defines the position of these restriction devices and is connected to a plurality of sensors which measure different variables such as ambient air and intake air temperatures.
However, the inventors herein have recognized potential issues with such systems. Specifically, the above control of restriction devices in response to intake or ambient air temperature may reduce the overall level of condensate, while potentially resulting in increased vehicle drag and engine over temperature conditions. Maintaining temperatures at a certain level such that condensate formation is low may result in keeping the restriction devices closed or open for long periods of time. If restriction devices are closed for a prolonged period, this may result in an increase in engine temperatures over optimal levels. Conversely, if the devices are open for a prolonged period, increased air flow is received through the vehicle front end, increasing the aerodynamic drag on the vehicle.
In one example, the above issues may be addressed by a method for controlling grille shutter orientation in response to engine cooling parameters, condensate formation in the CAC, and non-driven vehicle conditions, such as deceleration. In this way, it is possible to not only address condensate formation in the CAC, but also allow for adequate engine cooling and optimization of vehicle fuel economy. For example, the inventors herein have identified approaches that enable the grille shutters to still be adjusted in a way that improves fuel economy (by reducing drag), but that also maintains engine coolant temperature control to avoid over temperature and reduces condensate formation.
Specifically, it may be possible to pre-cool the engine coolant during a deceleration by opening the grille shutters so that subsequent acceleration operation can maintain the grille shutters closed for a longer duration, without resulting in over temperature conditions of the coolant. However, such pre-cooling operation may also exacerbate the potential for condensate formation, as the charge air cooler may be cooled to a greater extent. Therefore, in one example, the grill shutters may be adjusted responsive to condensate formation during the deceleration conditions to still enable pre-cooling of the engine coolant (and thus subsequent fuel economy gains during acceleration), while reducing condensate formation. In one example, grille shutter position may be adjusted based on current or forecasted weather conditions in order to more accurately identify condensate conditions, and thus effectively reduce condensate formation.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.